Adult neural stem cells with the ability to generate neurons and glia cells are active throughout life in both the dentate gyrus (DG) and the subventricular zone (SVZ). Differentiation of adult neural stem cells is induced by cell fate determinants like the transcription factor Prox1. Evidence has been provided for a function of Prox1 as an inducer of neuronal differentiation within the DG. We now show that within the SVZ Prox1 induces differentiation into oligodendrocytes. Moreover, we find that loss of Prox1 expression in vivo reduces cell migration into the corpus callosum, where the few Prox1 deficient SVZ-derived remaining cells fail to differentiate into oligodendrocytes. Thus, our work uncovers a novel function of Prox1 as a fate determinant for oligodendrocytes in the adult mammalian brain. These data indicate that the neurogenic and oligodendrogliogenic lineages in the two adult neurogenic niches exhibit a distinct requirement for Prox1, being important for neurogenesis in the DG but being indispensable for oligodendrogliogenesis in the SVZ. STEM CELLS 2016;34:2115-2129 SIGNIFICANCE STATEMENTIn the submitted study, we address the function of the homeobox transcription factor Prox1 for the specification of oligodendrocyte cell fate in adult neural stem cells. A function of Prox1 for neurogenesis is well described in Drosophila. Additionally, recently its implication in neuronal differentiation in neural stem cells has been shown. Therefore, the function seemed to be totally conserved from Drosophila to mammals. However, we here show that the function of Prox1 depends on the regional identity of the investigated neural stem cells. In neural stem cells of the hippocampus, Prox1 induces neuronal differentiation. However, in neural stem cell from the subventricular zone Prox1 induces differentiation in oligodendrocytes.

Depolarization drives neuronal plasticity. However, whether depolarization drives sensitization of peripheral nociceptive neurons remains elusive. By high-content screening (HCS) microscopy, we revealed that depolarization of cultured sensory neurons rapidly activates protein kinase A type II (PKA-II) in nociceptors by calcium influx through CaV1.2 channels. This effect was modulated by calpains but insensitive to inhibitors of cAMP formation, including opioids. In turn, PKA-II phosphorylated Ser1928 in the distal C terminus of CaV1.2, thereby increasing channel gating, whereas dephosphorylation of Ser1928 involved the phosphatase calcineurin. Patch-clamp and behavioral experiments confirmed that depolarization leads to calcium- and PKA-dependent sensitization of calcium currents ex vivo and local peripheral hyperalgesia in the skin in vivo. Our data suggest a local activity-driven feed-forward mechanism that selectively translates strong depolarization into further activity and thereby facilitates hypersensitivity of nociceptor terminals by a mechanism inaccessible to opioids.

Nociceptors are specialized sensory neurons that initiate the perception of pain. We applied high content screening microscopy to screen animal venoms for toxins, which activate pain enhancing signal transduction in sensory neurons. We identified the scorpion α‐toxin MeuNaTxα‐1 from Mesobuthus eupeus, which selectively affected tetrodotoxin‐sensitive voltage‐gated sodium channels, in particular NaV1.2, and thereby depolarized the nociceptors, leading to calcium influx, subsequent PKA‐II activation, and thermal hyperalgesia.

The WAVE regulatory complex (WRC) is the major Arp2/3 activator, promoting lamellipodial protrusions in migrating cells. The WRC is basally inactive but can be activated by Rac1 and phospholipids, and phosphorylation. However, the in vivo relevance of phosphorylation of WAVE remains largely unknown. Here, we identified the kinase CK1α as a novel regulator of WAVE controlling cell shape and cell motility in Drosophila macrophages. CK1α binds and phosphorylates WAVE in vitro. Phosphorylation of WAVE by CK1α appears not to be required for activation but rather regulates its stability. Pharmacologic inhibition of CK1α promotes ubiquitin-dependent degradation of WAVE. Consistently, loss of ck1α but not ck2 function phenocopies WAVE depletion. Phosphorylation-deficient mutations in the CK1α consensus sequences within the VCA domain of WAVE can neither rescue mutant lethality nor lamellipodia defects. By contrast, phosphomimetic mutations rescue all cellular and developmental defects. Finally, RNAi-mediated suppression of 26S proteasome or E3 ligase complexes substantially rescues lamellipodia defects in CK1α depleted macrophages. Thus, we conclude that the basal phosphorylation of WAVE by CK1α protects it from premature ubiquitin-dependent degradation, thus promoting WAVE function in vivo.